class_docstr: A singleton to track whether _TrackedCoder.encode/decode is called.
class_docstr_tok: ["A","singleton","to","track","whether","_TrackedCoder.encode\/decode","is","called","."]
code: def __new__(cls):
      if cls._instance is None:
          cls._instance = object.__new__(cls)
          cls._instance.reset()
      return cls._instance
  
file_path: data-validation/tensorflow_data_validation/types_test.py
imports: from absl.testing import absltest
  import apache_beam
  from apache_beam.testing import util
  import pyarrow
  from tensorflow_data_validation import types
label_desc: Use image node_id 2 for calling the _Tracker obj's underlying member method code with example usage: obj.__new__(cls) and returns: cls